U.S. patent application number 16/313784 was filed with the patent office on 2019-05-23 for information obtaining apparatus and control method for signal processing apparatus.
The applicant listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Nobuhito Suehira.
Application Number | 20190150757 16/313784 |
Document ID | / |
Family ID | 59298498 |
Filed Date | 2019-05-23 |
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United States Patent
Application |
20190150757 |
Kind Code |
A1 |
Suehira; Nobuhito |
May 23, 2019 |
INFORMATION OBTAINING APPARATUS AND CONTROL METHOD FOR SIGNAL
PROCESSING APPARATUS
Abstract
An information obtaining apparatus includes a comparison unit
configured to compare characteristic information in a first region
in an image corresponding to object information with characteristic
information in a second region that is different from the first
region and a display control unit configured to display information
based on a result of the comparison on a display unit.
Inventors: |
Suehira; Nobuhito; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
|
JP |
|
|
Family ID: |
59298498 |
Appl. No.: |
16/313784 |
Filed: |
June 22, 2017 |
PCT Filed: |
June 22, 2017 |
PCT NO: |
PCT/JP2017/022972 |
371 Date: |
December 27, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/489 20130101;
A61B 5/14546 20130101; A61B 5/0095 20130101; A61B 5/14542 20130101;
A61B 5/02007 20130101; A61B 5/1075 20130101; A61B 5/743
20130101 |
International
Class: |
A61B 5/02 20060101
A61B005/02; A61B 5/00 20060101 A61B005/00; A61B 5/145 20060101
A61B005/145; A61B 5/107 20060101 A61B005/107 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 30, 2016 |
JP |
2016-130603 |
Claims
1. An information obtaining apparatus that obtains object
information based on an acoustic wave propagated from an object
irradiated with light, the information obtaining apparatus
comprising: a comparison unit configured to compare characteristic
information in a first region in an image corresponding to the
object information with characteristic information in a second
region that is different from the first region; and a display
control unit configured to display information based on a result of
the comparison on a display unit.
2. The information obtaining apparatus according to claim 1,
wherein the characteristic information in the first region and the
characteristic information in the second region are function
information of the object.
3. The information obtaining apparatus according to claim 1,
wherein the first region and the second region are blood vessels of
the object.
4. The information obtaining apparatus according to claim 3,
wherein the first region and the second region correspond to
different parts of the same blood vessel.
5. The information obtaining apparatus according to claim 3,
wherein one of the first region and the second region is an artery
and the other one is a vein.
6. The information obtaining apparatus according to claim 5,
wherein the comparison unit further determines types of the blood
vessels in the first region and the second region, and the display
control unit further displays the types of the blood vessels in the
first region and the second region on the display unit.
7. The information obtaining apparatus according to claim 6,
wherein the comparison unit determines the types of the blood
vessels in the first region and the second region on the basis of a
histogram of the characteristic information in the first region and
the second region.
8. The information obtaining apparatus according to claim 3,
wherein the first region and the second region are the blood
vessels located at equivalent depths.
9. The information obtaining apparatus according to claim 1,
wherein the characteristic information in the first region and the
characteristic information in the second region are at least one of
oxygen saturations and hemoglobin amounts in the respective
regions, and a length, an area, and a volume of a structure in the
object.
10. The information obtaining apparatus according to claim 1,
wherein the display control unit displays plural pieces of
characteristic information with regard to the first region and the
second region on the display unit.
11. The information obtaining apparatus according to claim 1,
wherein the display control unit displays a type of a disease on
the display unit as the information based on the result of the
comparison.
12. The information obtaining apparatus according to claim 1,
further comprising an input unit configured to accept
specifications of the first region and the second region from the
object information.
13. A control method for a signal processing apparatus that
processes a signal based on an acoustic wave propagated from an
object irradiated with light, the control method comprising:
displaying an image of the object based on the acoustic wave on a
display unit; and displaying, when a first region and a second
region in the displayed image are specified, information based on a
comparison of characteristic information in the first region and
the second region on the display unit.
14. The control method for the signal processing apparatus
according to claim 13, wherein the image of the object is an image
indicating function information of the object.
15. The control method for the signal processing apparatus
according to claim 13, wherein the first region and the second
region are blood vessels, the control method further comprising
displaying of types of the blood vessels in the first region and
the second region.
16. The control method for the signal processing apparatus
according to claim 13, further comprising accepting the
specifications of the first region and the second region in the
image.
17. The control method for the signal processing apparatus
according to claim 13, further comprising varying the display in a
case where the information based on the comparison of the
characteristic information is not within a range of a predetermined
value from the display in a case where the information is within
the range of the predetermined value.
18. The control method for the signal processing apparatus
according to claim 13, wherein a type of a disease is displayed on
the display unit as the information based on the comparison in the
displaying the information based on the comparison.
19. The control method for the signal processing apparatus
according to claim 13, wherein, in a case where the result of the
comparison satisfies a predetermined condition, a part where the
predetermined condition is satisfied and the other part are
displayed by using different display methods on the display unit in
the displaying the information based on the comparison.
20. The control method for the signal processing apparatus
according to claim 13, wherein the characteristic information in
the first region and the characteristic information in the second
region are at least one of oxygen saturations and hemoglobin
amounts in the respective regions, and a length, an area, and a
volume of a structure in the object.
Description
TECHNICAL FIELD
[0001] The present invention relates to an information obtaining
apparatus that obtains object information based on an acoustic wave
propagated from an object irradiated with light and a control
method for a signal processing apparatus.
BACKGROUND ART
[0002] In recent years, photoacoustic tomography (hereinafter,
which will be also referred to as PAT) has been proposed as one of
optical imaging technologies. This principle is as follows. First,
an object is irradiated with pulsed light, and the light is
propagated and diffused in the object. An absorbent in the object
absorbs its light energy. The absorbent that has absorbed the light
energy performs thermal expansion and generates an acoustic wave.
This acoustic wave is referred to as a photoacoustic wave in the
present specification. The generated photoacoustic wave is detected
by an acoustic wave detecting element. Subsequently, reconstruction
processing is performed by using a signal based on the
photoacoustic wave detected by the acoustic wave detecting element,
and it is possible to obtain a photoacoustic image.
[0003] PTL 1 discloses a photoacoustic image apparatus that uses
near infrared light. The near infrared light is easily absorbed
into blood. For this reason, it is possible to obtain information
related to a distribution of blood vessels in the object. In
addition, it is possible to obtain information related to an oxygen
saturation of the blood vessel from signals obtained by using
respective lights of a plurality of wavelengths.
CITATION LIST
Patent Literature
[0004] PTL 1: Japanese Patent Laid-Open No. 2014-94225
SUMMARY OF INVENTION
Technical Problem
[0005] The photoacoustic image apparatus can obtain the
distribution and oxygen saturation of the blood vessels in the
above-described manner. However, the photoacoustic image apparatus
does not accurately calculate the oxygen saturation if a background
optical coefficient in the object is not specified. Since a living
matter is constituted by various tissues such as a skin surface, a
fat layer, a muscle layer, and the blood vessels, it is difficult
to accurately measure the background optical coefficient.
[0006] For this reason, a photoacoustic image apparatus is demanded
which can perform a diagnosis support even in a case where the
background optical coefficient is not accurately specified. The
present invention provides a technique with which a diagnosis by an
operator may be supported even in a case where the background
optical co-efficient is not accurately obtained.
[0007] An information obtaining apparatus that obtains object
information based on an acoustic wave propagated from an object
irradiated with light according to an aspect of the present
invention includes a comparison unit configured to compare
characteristic information in a first region in an image
corresponding to the object information with characteristic
information in a second region that is different from the first
region, and a display control unit configured to display
information based on a result of the comparison on a display
unit.
[0008] A control method for a signal processing apparatus according
to another aspect of the present invention includes displaying an
image of an object based on an acoustic wave propagated from an
object irradiated with light on a display unit, and displaying,
when a first region and a second region in the displayed image are
specified, information based on a comparison of characteristic
information in the first region and the second region on the
display unit.
[0009] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1A is a block diagram illustrating a configuration of a
photoacoustic image apparatus according to a first embodiment.
[0011] FIG. 1B is a block diagram illustrating a configuration of
the photoacoustic image apparatus according to the first
embodiment.
[0012] FIG. 2 is a flow chart according to the first
embodiment.
[0013] FIG. 3A is a schematic diagram of a blood vessel according
to the first embodiment.
[0014] FIG. 3B is a schematic diagram of the blood vessel according
to the first embodiment.
[0015] FIG. 3C is a schematic diagram of the blood vessel according
to the first embodiment.
[0016] FIG. 4 is a flow chart for identifying an artery and a vein
according to the first embodiment.
[0017] FIG. 5A is a flow chart for discriminating a blood vessel
type according to the first embodiment.
[0018] FIG. 5B is a flow chart for determining the blood vessel
type according to the first embodiment.
[0019] FIG. 5C is a flow chart for determining the blood vessel
type according to the first embodiment.
[0020] FIG. 6 illustrates a display example of a diagnostic index
according to the first embodiment.
[0021] FIG. 7 is a schematic diagram illustrating a blood vessel of
a breast according to a second embodiment.
[0022] FIG. 8A illustrates a display example of the diagnostic
index according to the second embodiment.
[0023] FIG. 8B illustrates a display example of the diagnostic
index according to the second embodiment.
[0024] FIG. 9 illustrates a display example of a circular chart
according to the second embodiment.
DESCRIPTION OF EMBODIMENTS
First Embodiment
Photoacoustic Image Apparatus
[0025] FIGS. 1A and 1B illustrate an information obtaining
apparatus according to a first embodiment of the present invention.
According to the present embodiment, the information obtaining
apparatus is a photoacoustic apparatus using a photoacoustic effect
which is configured to obtain information of the inside of the
object on the basis of an acoustic wave propagated from an object
irradiated with light. FIG. 1A mainly illustrates a cross sectional
view of a probe unit of the photoacoustic apparatus and also
schematically illustrates parts related to the probe unit and a
control unit. FIG. 1B is a plan view while a probe unit P is viewed
from the top (z-axis negative direction in the drawing).
[0026] The probe unit P includes 512 acoustic wave detecting
elements 102 arranged in a spiral manner along an inner surface of
a hemispherical container 101 that functions as a supporting
member. Furthermore, an opening 105 through which measurement light
from a light source unit 103 passes is formed at a bottom part of
the container 101. The measurement light is guided to the opening
105 by using a light guiding member such as a mirror or an optical
fiber, and the object held by a holding member 106 is irradiated
with the measurement light. In the present example, the measurement
light is emitted from the z-axis negative direction to a z-axis
positive direction. A material such as polyethylene terephthalate
having a strength for supporting the object and also having a
characteristic for transmitting light and acoustic waves is
preferably used for the holding member 106. It should be noted that
the inside of the container 101 and the inside of the holding
member 106 are filled with an acoustic matching material (for
example, water or castor oil) when necessary. It should be noted
that the container 101 may have any shape as long as a
configuration is adopted in which the acoustic wave detecting
elements 102 can be supported such that directions where
sensitivities of the plurality of acoustic wave detecting elements
is high concentrate in a certain region. For example, the shape
does not necessarily need to be hemispherical. The shape may be
spherical crown shape or an ellipsoid and also may be a bowl shape
formed by connecting a plurality of planes.
[0027] A relative positional relationship between the container 101
and the object can be changed by an XY stage which is illustrated
in the drawings. For this reason, when the container 101 is moved
by the XY stage, the object can be irradiated with pulsed light at
a plurality of relative positions with respect to the object.
Photoacoustic waves generated from the object at the respective
positions are converted into electric signals by the acoustic wave
detecting elements 102. The electric signals are stored by a data
obtaining unit 107, and reconstruction is performed by a data
processing unit 109 by using the stored data, so that it is
possible to obtain a three-dimensional photoacoustic image. The
data processing unit 109 realizes a function as a comparison unit.
Ultrasonic measurement used for form measurement can be performed
by an ultrasonic probe 104. The ultrasonic probe 104 has a
configuration in which the relative position with respect to the
object can be changed by the XY stage together with the container
101. The ultrasonic probe 104 is not limited to a linear type, and
configurations appropriate to its use such as a two-dimensional
array or a 1.5D array can be used.
[0028] A control unit 108 performs instructions related to control
on the entire apparatus such as light emission of the light source
unit 103, reception control of the data obtaining unit 107,
movement of the XY stage, and transmission and reception of the
ultrasonic wave by the ultrasonic probe 104. The control unit 108
is provided with a user interface as an input unit configured to
accept an input from an operator. The control unit 108 can execute
change of a measurement parameter, start and end of a measurement,
selection of a processing method for an image, saving of patient
information and the image, data analysis, and the like on the basis
of the instructions from the operator. Furthermore, detailed data
processing is performed by the data processing unit 109, and a
photoacoustic image, an oxygen saturation image, and a diagnostic
index obtained as the result is displayed on a display unit 110
functioning as a display unit.
Light Source Unit
[0029] A high-power laser light source is preferably used as the
light source of the light source unit 103 such that light reaches a
deep part of the object. It should be noted however that a light
emitting diode, a flash lamp, or the like may also be used. Various
types of lasers such as a solid-state laser, a gas laser, a dye
laser, and a semiconductor laser can be used as the laser. To
effectively generate the photoacoustic wave, the light irradiation
is preferably performed in a sufficiently short period of time in
accordance with a heat characteristic of the object. For this
reason, in a case where the object is a living matter, a pulse
width of the pulsed light generated from the light source is
preferably approximately 10 to 50 nanoseconds. In addition, a
wavelength of the pulsed light is preferably a wavelength at which
the light propagates to the inside of the object. Specifically, in
the case of the living matter, light having a wavelength of 700 nm
or higher but 1100 nm or lower is preferably used.
[0030] Herein, a titanium-sapphire laser corresponding to the
solid-state laser is used, and light having two wavelengths of 760
nm and 800 nm is used as the measurement light. When the light
having the plurality of wavelengths is used, an oxygen saturation
can be calculated by using a difference in absorption coefficients
for each wavelength. It should be noted that an irradiation timing,
the wavelengths, the strength, and the like of the light are
controlled by the control unit 108. The laser can alternately emit
the light having the two wavelengths respectively at 10 Hz. As a
result, the object is irradiated with the light at 20 Hz.
Acoustic Wave Detecting Element for Photoacoustic Wave
[0031] The acoustic wave detecting element 102 is an element
configured to receive the photoacoustic wave. Herein, a capacitive
micromachined ultrasound transducer (CMUT) is used. The acoustic
wave detecting element 102 is a single element having an opening of
.phi.3 mm and a high sensitivity with respect to a band of 0.5 MHz
to 5 MHz. Specifically, it means that the sensitivity in the range
of 0.5 MHz to 5 MHz of the acoustic wave detecting element becomes
a sensitivity that is half or more of the maximum value of the
element. Since the band having the high sensitivity includes a low
frequency, it is possible to obtain a satisfactory image even in
the case of the blood vessel having a thickness of approximately 3
mm. That is, a situation hardly occurs where the inside of the
blood vessel is missing and the blood vessel is observed like a
ring. 2048 sampling is performed while a sampling frequency is set
as 40 MHz. In addition, the data is set as signed 12-bit data.
[0032] The signal converted into the electric signal by the
acoustic wave detecting elements 102 is transmitted to the data
obtaining unit 107, amplified by an amplifier, converted into a
digital signal by an analog-to-digital (A/D) converter, and
temporarily saved as the data. Thereafter, the data is transmitted
to the control unit 108. It should be noted that a reception timing
of the acoustic wave is controlled by the control unit 108 so as to
be synchronized with the light irradiation.
[0033] It should be noted that the acoustic wave detecting element
102 is not limited to the CMUT and may also be constituted by an
element using a piezoelectric material.
Ultrasonic Probe
[0034] The ultrasonic probe 104 performs transmission and reception
of the ultrasonic wave and can obtain a form image or a Doppler
image. Piezoelectric ceramic (PZT) can be used as the element
constituting the ultrasonic probe 104. For example, the number of
elements is 256, and the band having the sensitivity is 5 MHz to 10
MHz. In addition, 2048 sampling is performed while the sampling
frequency is set as 40 MHz.
Data Processing Unit
[0035] The data processing unit 109 generates the photoacoustic
image of the inside of the object and the oxygen saturation image
corresponding to an image related to the function information
(function image) by the image reconstruction using the
photoacoustic signal. In addition to the above, desired processing
such as light quantity calculation, information processing used for
obtaining a background optical coefficient, or signal correction is
executed. The data processing unit 109 can be constituted by an
information processing apparatus provided with a processor, a
memory, and the like. Respective functions of the data processing
unit can be realized by respective modules of a program operated by
the processor. The data processing unit 109 is a block that
realizes a function as the comparison unit. As will be described
below, comparison of characteristic information such as an oxygen
saturation, a blood vessel diameter, a hemoglobin amount, or a
hemoglobin concentration in a plurality of regions is performed.
Furthermore, the data processing unit 109 also realizes a function
as a display control unit configured to display information based
on the comparison of the characteristic information, the
photoacoustic image, and the like on the display unit 110.
[0036] The photoacoustic image or the oxygen saturation image is
displayed on a display corresponding to the display unit 110. A
device having a size of 30 inches or larger which can perform color
display at a high resolution and having a contrast ratio of 1000:1
or higher is preferably used as the display.
Image Reconstruction
[0037] The image reconstruction is performed by the data processing
unit 109. A reconstruction technique such as a universal
back-projection method or a phasing addition method is used for the
image reconstruction. Herein, a case where the universal
back-projection method is used will be described as an example. An
initial acoustic pressure distribution P(r) generated by the
photoacoustic measurement is represented as Expression 1.
P ( r ) = .intg. .OMEGA. 0 b ( r 0 , t = r - r 0 ) d .OMEGA. 0
.OMEGA. 0 [ Math . 1 ] ##EQU00001##
[0038] A term b(r.sub.0, t) equivalent to projection data at this
time is represented as Expression 2. Herein, p.sub.d(r.sub.0)
denotes a photoacoustic signal detected by the acoustic wave
detecting element 102, r.sub.0 denotes positions of the respective
detecting elements, t denotes a time, and .OMEGA..sub.0 denotes a
solid angle of the acoustic wave detecting element 102. When the
data obtained by the data obtaining unit 107 is processed on the
basis of Expression 1, it is possible to obtain the initial
acoustic pressure distribution P(r).
b ( r 0 , t ) = 2 p d ( r 0 , t ) - 2 t .differential. p d ( r 0 ,
t ) .differential. t [ Math . 2 ] ##EQU00002##
[0039] Next, an absorption coefficient distribution can be
calculated from the initial acoustic pressure distribution P(r). An
acoustic pressure P(r) generated when the absorbent is irradiated
with the light is represented as Expression 3.
P(r)=.GAMMA..mu..sub.a(r).PHI.(r) [Math.3]
[0040] .GAMMA. denotes a Gruneisen coefficient corresponding to an
elastic characteristic value.
[0041] The Gruneisen coefficient is obtained by dividing a product
of a volume expansion coefficient (.beta.) and a square of an
acoustic velocity (c) by a specific heat (Cp). .mu..sub.a denotes
an absorption coefficient at the absorbent. .PHI.(r) denotes a
quantity of light with which the absorbent is irradiated in a local
region. It is possible to obtain the absorption coefficient
distribution .mu..sub.a(r) by solving Expression 3 in terms of the
absorption coefficient. It should be noted that the background
optical coefficient does not appear in the absorption coefficient
distribution since the background optical coefficient is
sufficiently lower than the absorption coefficient of the
absorbent.
[0042] The light quantity .PHI.(r) can be represented by using a
variable z as in Expression 4, for example, in a case where the
light quantity uniformly attenuates in a depth direction.
.PHI.=.PHI..sub.0EXP(-.mu..sub.effz) [Math.4]
[0043] .PHI..sub.0 denotes a light quantity of incident light on
the surface. .mu..sub.eff denotes an average equivalent damping
coefficient in the object and reflects a background scattering
coefficient .mu..sub.bs in the object and an absorption coefficient
.mu..sub.ba. For example, the average equivalent damping
coefficient is represented as Expression 5.
.mu..sub.eff= {square root over (3.mu..sub.ba.mu..sub.bs)}
[Math.5]
[0044] It should be noted that the background scattering
coefficient in the object and the absorption coefficient can be
measured, for example, by a near infrared spectrometry or the like.
In the near infrared spectrometry, the object is irradiated with
the light, and the light from the object is received. Subsequently,
a waveform of the signal is analyzed by a time domain or a
frequency domain to obtain the background optical coefficient.
These apparatuses perform the analysis by using a homogeneous
medium as a model. For this reason, it is difficult to accurately
measure the background optical coefficient of the living matter
constituted by various tissues such as a skin surface, a fat layer,
a muscle layer, and the blood vessels.
[0045] Next, a method of obtaining a hemoglobin distribution from
the absorption coefficient distribution will be illustrated. The
absorption coefficient .mu.a(.lamda.) of the absorbent is
determined by absorption of oxidized hemoglobin CHbO and reduced
hemoglobin CHbR per unit volume. When absorption coefficients of
the oxidized hemoglobin and the reduced hemoglobin are set as
EHbO(.lamda..sub.1), EHbR(.lamda..sub.1), EHbO(.lamda..sub.2), and
EHbR(.lamda..sub.2) at respective wavelengths, the absorption
coefficients are represented as Expression 6. It should be noted
that the left term is the absorption coefficient distribution
obtained by Expression 3.
.mu..sub.a(.lamda..sub.1)=.epsilon..sub.HbO(.lamda..sub.1)C.sub.HbO+.eps-
ilon..sub.HbR(.lamda..sub.1)C.sub.HbR
.mu..sub.a(.lamda..sub.2)=.epsilon..sub.HbO(.lamda..sub.2)C.sub.HbO+.eps-
ilon..sub.HbR(.lamda..sub.2)C.sub.HbR [Math.6]
[0046] When deformation from Expression 6 with regard to the
oxidized hemoglobin and the reduced hemoglobin is performed, the
oxidized hemoglobin and the reduced hemoglobin are respectively
represented as Expression 7.
C HbO = HbR ( .lamda. 2 ) .mu. a ( .lamda. 1 ) - HbR ( .lamda. 1 )
.mu. a ( .lamda. 2 ) HbO ( .lamda. 1 ) HbR ( .lamda. 2 ) - HbR (
.lamda. 1 ) HbO ( .lamda. 2 ) C HbR = HbO ( .lamda. 1 ) .mu. a (
.lamda. 2 ) - HbO ( .lamda. 2 ) .mu. a ( .lamda. 1 ) HbO ( .lamda.
1 ) HbR ( .lamda. 2 ) - HbR ( .lamda. 1 ) HbO ( .lamda. 2 ) [ Math
. 7 ] ##EQU00003##
[0047] It should be noted that, since the total hemoglobin (tHb) is
a total amount of the oxidized hemoglobin and the reduced
hemoglobin, the total hemoglobin is represented as Expression
8.
tHb=C.sub.HbO+C.sub.HbR [Math.8]
[0048] Since an oxygen saturation StO is a ratio of the oxidized
hemoglobin in the total hemoglobin, the oxygen saturation is
represented as Expression 9.
StO = C HbO C HbR + C HbO [ Math . 9 ] ##EQU00004##
Regarding Background Optical Coefficient
[0049] Here, an example of an experiment using a phantom will be
described with regard to an influence in a case where the
background optical coefficient is different from a true value. As
the phantom, nylon wires of .phi.1 mm respectively arranged at
depths of 10 mm and 20 mm as targets in urethane resin having the
scattering coefficient of 0.8/mm and the absorption coefficient of
0.004/mm comparable with values of human mammary gland tissues are
used. One nylon wire imitates the oxygen saturation of an artery
(for example, 95%), and the other nylon wire imitates the oxygen
saturation of a vein (for example, 80%). Adjustment of the oxygen
saturation can be realized by using a plurality of color materials
having different absorption coefficients depending on wavelengths.
The absorption coefficient of the nylon wire is set as 0.1/mm at
the wavelength of 800 nm comparable with blood.
[0050] In this case, if the value obtained by measuring the
background optical coefficient in the urethane resin varies from
the true value by 5%, the oxygen saturation at the depth of 20 mm
may vary by approximately 10%. As illustrated in Expression 4,
since the error of the oxygen saturation depends on the depth, the
error becomes larger as the depth becomes deeper. Therefore, in a
case where the background optical coefficient has the error, the
numeric value calculated as the oxygen saturation StO may exceed
100%.
[0051] On the other hand, in the case of the target imitating the
oxygen saturation of the artery and the target imitating the oxygen
saturation of the vein located at equivalent depths, a result
obtained by dividing the oxygen saturations of those tends to have
a constant value calculated irrespective of the depths where the
two targets are arranged. It is conceivable that this is because
the errors in the respective wavelengths are cancelled by the
division, and the influence becomes smaller.
Measurement and Signal Processing
[0052] FIG. 2 illustrates a flow chart for displaying the
diagnostic index related to the processing according to the present
embodiment.
[0053] In step S1, the measurement is started. In this state, the
object is inserted into the holding member 106 so as to be
contacted with each other. The holding member 106 and the object
are in close contact such that air does not exist between the
holding member 106 and the object, and the surrounding of the
object is filled with water corresponding to acoustic matching
liquid. It should be noted that the ultrasonic wave measurement may
be performed by the ultrasonic probe 104 before the photoacoustic
image is obtained. This is because coordinates of a lesioned part
of the object or the like are identified by the ultrasonic wave
image.
[0054] In step S2, the photoacoustic measurement is performed.
First, an operator issues a measurement instruction from the
control unit 108. As a result, the container 101 is moved to a
desired position by the XY stage. Subsequently, the pulsed light is
emitted from the light source unit 103, and in synchronism with
this, the acoustic wave detecting element 102 receives the
photoacoustic wave. With regard to the irradiation of the pulsed
light, while the container 101 is moved in a spiral manner, the
irradiation of the light having the two waveforms of 760 nm and 800
nm is alternately performed. Finally, the photoacoustic waves are
obtained at the respective wavelengths at a position of 1024.
Imaging ranges can be set as diameters of 80 mm, 120 mm, and 160 mm
by selection. It should be noted that the influence of the
positional shift between the wavelengths due to a body motion or
the like becomes smaller when the light having the different
wavelengths is alternately emitted to obtain the photoacoustic
image for the two wavelengths as compared with a case where the
measurement is performed throughout at one wavelength, and
thereafter the measurement is performed at the other wavelength.
That is, the above-described control method is more preferably used
to calculate the oxygen saturation.
[0055] In step S3, the function image is generated from the
photoacoustic image. The image reconstruction is performed from the
obtained data, and the initial acoustic pressure distribution for
each wavelength is obtained. Subsequently, the absorption
coefficient distribution can be obtained by using the
above-described expressions. The light quantity distribution can be
obtained by using the optical coefficient at which the object is
measured by the near infrared spectrometry and form information of
the holding member 106. It should be noted that the data of the
ultrasonic probe 104 may also be used as the form information.
Thereafter, the oxygen saturation image corresponding to the
function image is obtained. With regard to the oxygen saturation,
the oxygen saturation may be calculated in a part where the
absorption coefficient is higher than or equal to a threshold in
the absorption coefficient distribution instead of the calculation
over the specified entire region. That is, since the absorption
coefficient at the position where the blood vessel exists is higher
than the absorption coefficient at the position where the blood
vessel does not exist, it is possible to selectively display only
the oxygen saturation at the position of the blood vessel.
[0056] In step S4, a first region and a second region are selected.
The operator uses, for example, a user interface of the control
unit 108 on a screen to select the first region and the second
region from the oxygen saturation image corresponding to the
function image displayed on the display unit 110. FIGS. 3A to 3C
illustrate examples in which parts of the blood vessel in the
function image are set as the first region and the second region.
FIG. 3A illustrates a narrowed part 304 of the blood vessel. The
example is illustrated in which a first region 302 and a second
region 303 are set in different positions of this blood vessel
(that is, an upstream side and a downstream side of the narrowed
part). In FIG. 3B, the first region 302 is set in one of
accompanying artery 306 and vein 307, and the second region 303 is
set in the other of the accompanying artery 306 and vein 307. In
FIG. 3C, with regard to the blood vessel 308 having branches, the
first region 302 is set in one of the branches, and the second
region 303 is set in the other of the branches. A branched part
where the second region 303 is set has the blocked part 310. It
should be noted that, in the respective drawings of FIGS. 3A to 3C,
the first and second regions are illustrated as rectangular areas
in the blood vessel, but the specifications of the respective
regions are not limited to this technique. For example, when the
operator specifies a region wider than the width of the blood
vessel, the data processing unit 109 may extract a part equivalent
to the blood vessel in the region to be set as the first region or
the second region. As another method, when the operator specifies
an arbitrary position in the blood vessel, a predetermined range in
the blood vessel including the specified position may be set as the
first region or the second region. Furthermore, as still another
example, the data processing unit 109 may extract and automatically
set parts before and after the narrowed part of the blood vessel,
the accompanying blood vessel, or the branch of the blood vessel by
a technique such as pattern matching, or present the extracted
regions to the operator and ask the operator to select the first
and second regions.
[0057] In step S5, comparison of the characteristic information in
the first region 302 and the second region 303 is performed.
Examples of the characteristic information include the oxygen
saturation, the total hemoglobin amount, the blood vessel diameter,
and the like. The oxygen saturation and the total hemoglobin amount
are average values of the selected parts. The blood vessel diameter
305 is an average value of the blood vessel diameters where the
selected regions are included. The comparison of the characteristic
information is performed by dividing the characteristic information
in the first region by the characteristic information in the second
region. It should be noted that the comparison is not limited to
the division and can also be realized by the subtraction. However,
as described above, the division is preferably performed since the
error of the depth direction can be cancelled.
[0058] In step S6, a type of the blood vessel in the first region
302 and the second region 303 is discriminated. The type of the
blood vessel refers to types such as the artery and the vein.
Hereinafter, a flow for determining the type of the blood vessel
will be described with reference to FIG. 4. It should be noted that
the processing in step S6 may be executed in parallel with step
S5.
[0059] In step A1, processing of determining the type of the blood
vessel is started.
[0060] In step A2, the presence or absence of reference information
is determined. The reference information includes finding by a
doctor, anatomical structural information detected by the pattern
matching or the like performed by the data processing unit 109, a
result of Doppler measurement by the ultrasonic apparatus, and the
like. In a case where the reference information is present, the
flow proceeds to step A9, and the determination on the type of the
blood vessel is performed. On the other hand, in a case where the
input of the reference information is absent, the flow proceeds to
step A3, and the processing of determining the type of the blood
vessel is performed by using the oxygen saturation image obtained
from the photoacoustic image apparatus. The oxygen saturation image
is three-dimensional data including a desired blood vessel of FIGS.
3A to 3C in a range of 30 mm.times.30 mm.times.10 mm, for example.
This range may be specified by the operator or may be automatically
set by the data processing unit 109. In a case where the specified
range is not sufficiently large, there is a fear that a reliability
of a histogram generated in step A3 may not be sufficient. For this
reason, the data processing unit 109 can also support the operator
such that the sufficient reliability of the histogram generated in
the range set by the operator can be attained. For example, in a
case where the range specified by the operator is narrower than a
predetermined value, the range may be automatically expanded so
that the range is not set to be narrower than the predetermined
value.
[0061] In step A3, the data processing unit 109 generates the
histogram of the oxygen saturation from the oxygen saturation
image. FIGS. 5A to 5C schematically illustrate the histogram of the
oxygen saturation. The vertical axis represents the oxygen
saturation, and the horizontal axis represents the frequency. FIG.
5A illustrates an example in a case where the oxygen saturation is
accurately calculated. In this example, two peaks of the frequency
appear in positions having different oxygen saturations. It is
conceivable that first peak 503 in the position having the higher
oxygen saturation is derived from the artery, and a second peak 504
in the position having the lower oxygen saturation is derived from
the vein. FIG. 5B illustrates a case where the oxygen saturation is
calculated from a region at a certain depth from the surface. Since
the background optical coefficient is deviated from the actual
value, the oxygen saturation indicates a frequency distribution
different from the frequency distribution illustrated in FIG.
5A.
[0062] FIG. 5C illustrates a state in which a normal oxygen
saturation and an abnormal oxygen saturation exist in a mixed
manner. An example of the abnormal oxygen saturation includes a
case where oxygen supply from the blood vessel becomes insufficient
in the tumor part, and a hypoxic state is established. In a case
where the blood vessel is clogged because of narrowing or the like,
the oxygen saturation may be decreased, and a frequency
distribution as illustrated in FIG. 5C may be obtained.
[0063] In step A4, a determination on whether or not the histogram
is multi-modal. In a case where the normal artery and vein are
included in the specified region, the histogram becomes bimodal
having at least two peaks. In a case where the blood vessel in
which the oxygen saturation is decreased by the tumor or the
occlusion exists, the number of peaks may be further increased. For
this reason, since it is conceivable that the oxygen saturation can
be normally calculated when the histogram is multi-modal, the flow
proceeds to step A6. On the other hand, in the case of a unimodal
histogram, the flow proceeds to step A5.
[0064] In the case of the unimodal histogram, a case where the
blood vessel is not present in the measurement range, a case where
only one of the artery and the vein is present, and the like are
conceivable. In view of the above, according to the present
embodiment, in a case where the histogram is unimodal in step A4,
the operator is notified in step A5 that the reliability of the
obtained measurement result is low. After the notification to the
operator is performed, the processing may be ended. After the
notification for urging the operator to set the measurement range
again is performed, the processing in step A1 and subsequent steps
may also be performed.
[0065] In a case where it is determined in step A4 that the
histogram is multi-modal, it is determined in step A6 whether or
not the oxygen saturation in the histogram is within a
predetermined range. When the oxygen saturation is within the
predetermined range, the first peak 503 of the histogram is within
a 20% range 501 where a normal range 505 of the oxygen saturation
of the artery (for example, 93 to 99%) is set as a center, and the
second peak 504 of the histogram is within a 20% range 502 where a
normal range 506 of the oxygen saturation of the vein (for example,
73 to 77%) is set as a center. When the first peak 503 and the
second peak 504 are within the predetermined ranges, it is
conceivable that the oxygen saturation can be normally calculated,
and the flow proceeds to step A8. On the other hand, in a case
where at least one of the first peak 503 and the second peak 504 is
not within the predetermined range, the flow proceeds to step
A7.
[0066] It should be noted that the function information including
the oxygen saturation is more accurately calculated as the position
is closer to the surface of the object. For this reason, in a case
where it is determined that the value is not within the setting
value in the used range, whether or not the value is within the set
value in the range including the data in the vicinity of the
surface may be checked. In a case where the same segments exist in
left and right, a normal segment may be measured to check whether
or not the value is within the setting value. With this
configuration, it is possible to distinguish whether or not the
value of the optical coefficient has an error. It should be noted
that the range of the setting value may be changed in accordance
with the depth.
[0067] In step A7, predetermined display is performed. As a case
where the oxygen saturation is not within the predetermined range,
there is a possibility that the optical coefficient is not an
accurate value. In a case where the normal site is within the
setting value and a target site is not within the setting value,
cyanosis or the like is conceivable. For example, the oxygen
saturation of the artery of central cyanosis is 82% or lower, and
the oxygen saturation of the vein is 52% or lower, for example. In
addition, the oxygen saturation of the artery of peripheral
cyanosis is a normal value, and the oxygen saturation of the vein
is 33% or lower, for example. Furthermore, local peripheral
circulatory insufficiency may be generated due to arterial
occlusive disease or venous occlusive disease. Type of possible
diseases as described above may be displayed.
[0068] In step A8, the range of the artery and the vein is
identified. It is determined in which region in the function image
a group where the first region and the second region include the
first peak 503 and a group where the first region and the second
region include the second peak 504 are included. In the case of the
region corresponding to the group including the first peak 503, a
probability is high that this is the artery. In the case of the
region corresponding to the group including the second peak 504, a
probability is high that this is the vein.
[0069] In step A9, a determination is performed on which one of the
artery and the vein the first region and the second region selected
in step S4 respectively correspond to. The data processing unit 109
determines which one of the first region and the second region the
first region and the second region respectively correspond to on
the basis of the range of the artery and the vein identified in
step S8.
[0070] In step A10, the process flow for determining the type of
the blood vessel is ended, and the process flow proceeds to step S7
of FIG. 2.
[0071] In step S7, the diagnostic index that takes into account the
comparison result of the characteristic information obtained in
step S5 and the discrimination result of the type of the blood
vessel obtained in step S6 as described above is displayed. As
illustrated in FIG. 6, the type of the blood vessel, the oxygen
saturation, the total hemoglobin amount, the blood vessel diameter,
and the like are respectively displayed with respect to a region 1
and a region 2 as the diagnostic index, and furthermore, those
comparison results are displayed. The hemoglobin concentration in
the relevant region may be indicated instead of the total
hemoglobin amount or together with the total hemoglobin amount. The
comparison result is a ratio of numeric values in the respective
regions, for example. The diagnosis can be supported by displaying
these items.
[0072] For example, when attention is focused on the oxygen
saturation, since the oxygen saturations of the first region 302
and the second region 303 in the same blood vessel should be
matched with each other in a normal state, a ratio of those is 1.
However, in a case where the oxygen saturations are varied in the
parts before and after the narrowed part 304 as illustrated in FIG.
3A, if the ratio of the oxygen saturations is not in a range
between 0.98 and 1.02, for example, the blocking or narrowing of
the blood vessel is suspected. The range between 0.98 and 1.02 is
set as values that take the error into account. When attention is
focused on accompanying artery/vein as illustrated in FIG. 3B, the
ratio of the oxygen saturation of the artery to the oxygen
saturation of the vein in a normal state is 1.24 to 1.32. When a
result obtained by dividing the value of the artery by the value of
the vein is lower than 1.24, it is conceivable that the oxygen
saturation of the artery has an abnormality, and the blocking or
narrowing of the artery is suspected. On the other hand, when the
ratio is higher than 1.32, the hypoxic state is established, and
the tumor or narrowing is suspected. The same also applies when
attention is focused on the blood vessel that is not the
accompanying blood vessel. In FIG. 3C, the same blood vessel is
branched. Therefore, the ratio of the oxygen saturations of the
different branches becomes 1 in a normal state. Similarly as in the
case of FIG. 3A, while the error is taken into account, if the
ratio of the oxygen saturation of the first region to the oxygen
saturation of the second region is not the range between 0.98 and
1.02, the blocking or narrowing of the blood vessel is suspected.
In this manner, when the comparison of the characteristic
information of the different regions is performed, it is possible
to support the diagnosis by the operator.
[0073] Attention is focused on the hemoglobin concentration. When
the hemoglobin concentration is high, an increased viscosity of the
blood is suspected. When the hemoglobin concentration is low,
oxygen deficiency is suspected. Attention is focused on the blood
vessel thickness. In a case where a result is obtained that the
artery is narrow by the comparison of the blood vessel diameters of
the artery and the vein in the accompanying part, the blocking or
narrowing of the artery is suspected. It should be noted that the
comparison may also be displayed in each of the normal part and the
target part. The comparison may also be performed on the basis of
the area or volume of the blood vessel other than the blood vessel
thickness, that is, the blood vessel diameter.
[0074] The predetermined range is previously stored in a storage
unit of the data processing unit 109 with regard to the comparison
result of various characteristic information. In a case where the
comparison result obtained as the result of the measurement is not
within the predetermined range, the display is preferably performed
to facilitate the recognition of the operator while a color of a
column corresponding to this comparison result is set to be
different from a color of the other column, a size or type of a
font is set to be different from that of the other column, or
blinking is performed for the display. That is, the information can
be emphasized while the comparison result is displayed by different
display methods in a case where the comparison result satisfies a
predetermined condition and a case where the comparison result does
not satisfy the predetermined condition. Furthermore, in a case
where the comparison result is not within the predetermined range,
a name of a disease that may be suspected from the comparison
result can be presented. That is, the diagnosis by the operator is
supported by presenting the disease name corresponding to the
comparison result.
[0075] The data processing unit 109 may also display the comparison
result on the display unit 110 together with the function image.
When the operator specifies the first region and the second region
from among the function images while observing the function image
illustrated in FIGS. 3A to 3C, the comparison result of FIG. 6 may
be updated in accordance with the specification. Furthermore, a
third region different from the first region and the second region
may be specified to present the comparison result of the
characteristic information in the respective regions to the
operator.
[0076] As described above, according to the present embodiment,
even if the background optical coefficient is not an accurate
value, the information useful to the diagnosis on the presence or
absence of the tumor, the artery obstruction, the venous
obstruction, or the like is provided by displaying the information
of the type of artery/vein and the comparison result of the
characteristic information, and the diagnosis can be supported.
Second Embodiment
[0077] Another embodiment of the present invention will be
described. Descriptions will be omitted with regard to aspects
common to the first embodiment, and different aspects will be
mainly described.
[0078] According to the first embodiment, the first region and the
second region are set in the specific blood vessel. However, the
method for the setting of the respective regions is not limited to
this, and the first region and the second region may be regions
including a plurality of blood vessels.
[0079] FIG. 7 is a schematic diagram of an oxygen saturation image
701 of a breast in a range including a nipple 702. The artery is
indicated by a solid line, and the vein is indicated by a dotted
line. A state is illustrated in which a first region 703 and a
second region 704 are set in the oxygen saturation image 701. It
can be checked that the artery and the vein run through while the
nipple 702 is set as a center. It should be noted that, according
to the present embodiment, the nipple 702 is illustrated for
convenience of the descriptions, but the nipple 702 does not appear
in an image depending on a manner of displaying the image (such as
a range of a depth direction to be displayed).
[0080] According to the present embodiment, FIGS. 8A and 8B
illustrate an example of a table presented as the information based
on the comparison result. FIG. 8A illustrates the further
comparison of the characteristic information included in the region
of the artery and the region of the vein in the first region 703.
In this example, the table is constituted by the oxygen saturation,
the total hemoglobin amount, and the volume. An average value in
the region is calculated for the oxygen saturation and the total
hemoglobin amount. It should be noted that the hemoglobin
concentration of this region may be indicated instead of the total
hemoglobin amount or together with the total hemoglobin amount. The
volume is calculated by counting the number of pixels of the artery
or the vein. It should be noted that the discrimination of the
artery and the vein can be performed by using the technique
described according to the first embodiment. The group determined
as the artery by the histogram and the group determined as the vein
are respectively displayed, and with this configuration, it is
possible to perform the comparison of the artery and the vein in
the same region. With regard also to the second region 703, it is
possible to present the similar information.
[0081] FIG. 8B illustrates the result of the mutual comparison of
the arteries in the first region 703 and the second region 704.
Similarly, FIG. 8B illustrates the result of the mutual comparison
of the veins in the first region 703 and the second region 704.
With this configuration, it is possible to perform the mutual
comparison of the arteries or the mutual comparison of the veins in
the different regions.
[0082] The first region 703 and the second region 704 do not
necessarily need to be the photoacoustic image obtained by the
single measurement. For example, in the case of the breast, the
first region may be set in the right breast, and the second region
may be set in the left breast. If the tumor, aneurysm, varicose, or
the like exists in one of the regions, the comparison result of the
numeric values in the first region and the second region may
indicate a peculiar value. Since the characteristic information at
the equivalent depths can be compared, it is effective to detect
the abnormality.
[0083] In addition, the ratio of the oxygen saturations in the
first region and the second region in the vicinity of the surface
or the ratio of the oxygen saturations in the first region and the
second region in the vicinity of the desired depth may be
displayed. As already described above, since the ratio of the
oxygen saturations tends to be constant irrespective of the depth,
it is effective to detect the abnormality.
[0084] It should be noted that a circular chart as illustrated in
FIG. 9 may be used as the display method for the numeric values in
the respective regions. For example, with regard to the blood
vessel included in the first region, FIG. 9 can indicate
proportions respectively occupied by the artery 901 (equivalent to
the range 505 in FIG. 5A) indicating the normal oxygen saturation,
the artery 902 (equivalent to the part except for the range 501 to
the range 505 in FIG. 5A) indicating the value outside of the range
of the normal oxygen saturation, the vein 903 (equivalent to the
range 506 in FIG. 5A) indicating the normal oxygen saturation, the
vein 904 (equivalent to the part except for the range 502 to the
range 506 in FIG. 5A) indicating the value outside of the range of
the normal oxygen saturation, and the other 905 (equivalent to the
part except for the range 501 and the range 502 in FIG. 5A). When
respective circular charts in the first region and the second
region are compared with each other, it may be possible to visually
find out differences in the proportions. Furthermore, a division
image obtained by division of the oxygen saturation of the vein
with respect to the artery at the same depth may be newly created
and displayed.
[0085] As described above, according to the present embodiment,
even if the background optical coefficient is not an accurate
value, the information useful to the diagnosis is provided, and the
diagnosis can be supported.
Third Embodiment
[0086] Still another embodiment of the present invention will be
described. Descriptions will be omitted with regard to aspects
common to the above-described embodiments, and different aspects
will be mainly described.
[0087] According to the present embodiment, in accordance with the
specification of a certain region in the object by the operator of
the photoacoustic image apparatus, the comparison of the
characteristic information of the artery and the vein in the
specified region is performed. For example, the operator specifies
the region in a state in which the oxygen saturation image 701 is
presented as illustrated in FIG. 7. The photoacoustic image
apparatus extracts the artery and the vein included in the
specified region in response to this specification and executes the
comparison processing of the characteristic information of the
artery and the vein in this region to display the result on the
display unit. The technique described according to the first
embodiment can be used for the discrimination on the artery and the
vein. In addition, the characteristic information to be compared is
also as described above.
[0088] According to the first embodiment, the operator selects the
first region 302 and the second region 303 in the example described
with reference to FIG. 3B. In contrast to this, according to the
present embodiment, when the operator specifies the region
including the target artery and vein without individually
specifying the blood vessel, the photoacoustic image apparatus
discriminates the artery and the vein included in the region and
executes the comparison processing of the characteristic
information of the artery and the vein. For this reason, it is more
facilitated for the operator to obtain the comparison result of the
characteristic information.
[0089] It should be noted that the characteristic information and
the comparison method illustrated according to the above-described
respective embodiments are merely for exemplifications and can be
modified in any forms in a range without departing from the
technical idea of the present invention. For example, according to
the respective embodiments, the case has been described where the
first region and the second region are specified from the oxygen
saturation image corresponding to the function image, but the first
and second regions may also be specified from the initial acoustic
pressure distribution image or the absorption coefficient
distribution image obtained by using light having one wavelength.
That is, the first and second regions may be specified from any
image as long as the image corresponding to the object
information.
[0090] In addition, the descriptions have been given while the
blood vessel is used as the example according to the
above-described respective embodiments, but the present invention
can also be applied to structures other than the blood vessel.
[0091] According to the embodiments of the present invention, even
in a case where the background optical coefficient of the object is
not accurately obtained, it is possible to perform the diagnosis
support.
[0092] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
Other Embodiments
[0093] Embodiment(s) of the present invention can also be realized
by a computer of a system or apparatus that reads out and executes
computer executable instructions (e.g., one or more programs)
recorded on a storage medium (which may also be referred to more
fully as a `non-transitory computer-readable storage medium`) to
perform the functions of one or more of the above-described
embodiment(s) and/or that includes one or more circuits (e.g.,
application specific integrated circuit (ASIC)) for performing the
functions of one or more of the above-described embodiment(s), and
by a method performed by the computer of the system or apparatus
by, for example, reading out and executing the computer executable
instructions from the storage medium to perform the functions of
one or more of the above-described embodiment(s) and/or controlling
the one or more circuits to perform the functions of one or more of
the above-described embodiment(s). The computer may comprise one or
more processors (e.g., central processing unit (CPU), micro
processing unit (MPU)) and may include a network of separate
computers or separate processors to read out and execute the
computer executable instructions. The computer executable
instructions may be provided to the computer, for example, from a
network or the storage medium. The storage medium may include, for
example, one or more of a hard disk, a random-access memory (RAM),
a read only memory (ROM), a storage of distributed computing
systems, an optical disk (such as a compact disc (CD), digital
versatile disc (DVD), or Blu-ray Disc (BD).TM.), a flash memory
device, a memory card, and the like.
[0094] This application claims the benefit of Japanese Patent
Application No. 2016-130603, filed Jun. 30, 2016, which is hereby
incorporated by reference herein in its entirety.
* * * * *